how to skip blocks of text when writing file in python

Question

Is it possible to use python to skip blocks of text when writing a file from another file?

For example lets say the input file is:

This is the file I would like to write this line
I would like to skip this line
and this one...
and this one...
and this one...
but I want to write this one
and this one...

How can I write a script that allows me to skip certain lines that differ in content and size which resumes writing the lines to another file once it recognizes a certain line?

My code reads through the lines, doesn't write duplicate lines and performs some operation on the line by using dictionaries and regex.

Answer 1

Pseudo-code:

# Open input and output files, and declare the unwanted function
for line in file1:
    if unwanted(line):
        continue
    file2.write(line)
# Close files etc...

Answer 2

You can read the file line by line, and have control on each line you read:

with open(<your_file>, 'r') as lines:
    for line in lines:
        # skip this line
        # but not this one

Note that if you want to read all lines despite the content and only then manipulate it, you can:

with open(<your_file>) as fil:
    lines = fil.readlines()

Answer 3

This should work:

SIZE_TO_SKIP = ?
CONTENT_TO_SKIP = "skip it"

with open("my/input/file") as input_file:
    with open("my/output/file",'w') as output_file:
        for line in input_file:
            if len(line)!=SIZE_TO_SKIP and line!=CONTENT_TO_SKIP:
                output_file.write(line)